Magnetic memory device and method for production thereof

ABSTRACT

A magnetic memory device in which the memory cell of MRAM is reduced in size, and a method for producing the magnetic memory device are provided. The lower wiring is formed below the word line. The connecting hole and the plug connected to it are provided. The reading wiring and the lower layer wiring are connected through this plug. Alternatively, the local wiring is provided in the connecting hole and the reading wiring and the lower layer wiring are connected. In this way it is possible to form the connecting hole close to the word line, and hence it is possible to reduce the cell size in the direction along the bit line.

The present application is a continuation of U.S. Ser. 11/007,381, nowU.S. Pat. No. 7,095,650, issued on Aug. 22, 2006, filed Dec. 8, 2004,which claims priority to Japanese Patent Application No. 2003-416601filed Dec. 15, 2003, both of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a magnetic memory device and a methodfor production thereof. The magnetic memory device is a magnetic randomaccess memory (MRAM) of nonvolatile type consisting of memory elementseach having a magnetization pinned layer in which the direction ofmagnetization is pinned and a magnetic layer in which the direction ofmagnetization is variable, with one laid on top of the other.

The recent wide spread of information and communications equipment,particularly personal small ones such as portable terminals, requirestheir constituents (such as memory elements and logic elements) to haveimproved performance, including high integration, high speed, and lowpower consumption.

Particularly, non-volatile memory is regarded as indispensable in theage of ubiquitous computing because it preserves personal importantinformation in case of dead battery and network failure or serverbreakdown. Recent portable equipment is so designed as to reduce powerconsumption as much as possible by keeping idle circuit blocks instand-by mode. It would be possible to save power and memory if anon-volatile memory functioning as both high-speed work memory andhigh-capacity storage memory is realized. It would make the “instant-onfunction” feasible which permits equipment to start working instantly assoon as power is turned on.

Among non-volatile memory are flush memory, which relies onsemiconductors, and FRAM (ferroelectric random access memory), whichrelies on ferroelectric substances.

Flush memory is limited in writing speed to the order of microseconds.FRAM is also limited in the number of rewriting cycles to 10¹² to 10¹⁴,that is, it is too poor in endurance to replace SRAM (static randomaccess memory) and DRAM (dynamic random access memory). Moreover, itpresents difficulties in microprocessing of ferroelectric capacitorstherein.

There is noteworthy non-volatile memory free of these disadvantages,which is magnetic memory called MRAM (Magnetic Random Access Memory).MRAM in the early stage is one which is based on spin valve. It utilizesthe AMR (Anisotropic Magneto Resistive) effect, which was reported by J.M. Daughton in “Thin Solid Films”, vol 216 (1992), pp. 162 to 168.Alternatively, it utilizes the GMR (Giant Magneto Resistance) effect,which was reported by D. D. Tang et al. in “IEDM Technical Digest”(1997), pp. 995 to 997. Unfortunately, they have the disadvantage thatthe memory cell has a low resistance of 10-100Ω which leads to a largepower consumption per bit for reading. This disadvantage makes itdifficult to realize a large-capacity memory.

There is another type of MRAM which utilizes the TMR (Tunnel MagnetoResistance) effect. It has come to attract attention because of itsremarkable increase in the rate of change in resistance from 1 to 2% atroom temperature (as reported by R. Meservey et al. in “PhysicsReports”, vol. 238, pp. 214 to 217, 1994) to nearly 20% (as reported byT. Miyazaki et al. in “J. Magnetism & Magnetic Material”, vol. 139,(L231), 1995).

MRAM is a semiconductor magnetic memory that relies on themagnetoresistance effect resulting from spin dependent conduction ofnanomagnetic substances. It is a non-volatile memory that retains memorywithout external power supply.

MRAM has such a simple structure that it can be highly integrated withease. It is capable of rewriting many times because it relies on therotation of magnetic moment for recording. It is also expected to have avery high access speed. In fact, its ability to run at 100 MHz has beenreported by R. Scheuerlein et al. in ISSCC Digest of Technical Papers,pp. 128 to 129, Feb. 2000.

MRAM is broadly divided into two types. One is cross-point type and theother is 1T1J type or 2T2J type. MRAM of cross-point type is disclosedin U.S. Pat. No. 5,640,343. MRAM of 1T1J type consists of one selectingelement and one TMR element. MRAM of 2T2J consists of two selectingelements and two TMR elements which are complementary to each other.

The MRAM consisting of one selecting element and one TMR element isshown in FIG. 33. The memory cell (or memory element) of MRAM is the TMRelement 10, which consists mainly of a supporting substrate 9 and amemory layer 2 (in which the direction of magnetization rotatescomparatively easily) and two magnetization pinned layers 4 and 6.

The magnetization pinned layer consists of a first magnetization pinnedlayer 4 and a second magnetization pinned layer 6. Between these twolayers is interposed a conducting layer 5 through which they are coupledantiferromagnetically.

The memory layer 2 and the magnetization pinned layers 4 and 6 areformed from a ferromagnetic material such as nickel, iron, cobalt, andalloys thereof. The conducting layer is formed from any of ruthenium,copper, chromium, gold, and silver. The second magnetization pinnedlayer 6 is in contact with the antiferromagnetic material layer 7, sothat it has a strong unidirectional magnetic anisotropy due to exchangeinteraction between these layers. The antiferromagnetic material layer 7may be formed from a manganese alloy with iron, nickel, platinum,iridium, or rhodium, or a cobalt oxide or nickel oxide.

Between the memory layer 2 (which is a magnetic layer) and the firstmagnetization pinned layer 4 is interposed a tunnel barrier layer 3formed from an insulating material such as an oxide or nitride ofaluminum, magnesium, or silicon. It cuts off the magnetic couplingbetween the memory layer 2 and the magnetic pinned layer 4, and it alsopermits tunnel current to flow. The magnetic layer and the conductorfilm are formed mainly by sputtering. The tunnel barrier layer 3 may beformed by oxidizing or nitriding the metal film which has been formed bysputtering. The top coat layer 1 prevents mutual diffusion between theTMR element 10 and the wiring connected thereto. It also reduces contactresistance and protects the memory layer 2 from oxidation. It is usuallyformed from Cu, Ta, or TiN. The underlying electrode layer 8 serves forconnection between the TMR element and a switching element connectedthereto in series. This underlying layer 8 may function also as theantiferromagnetic layer 7.

The memory cell constructed as mentioned above reads information bydetecting the change in tunnel current due to magnetoresistance effect(which will be described later). The magnetoresistance effect depends onthe relative direction of magnetization of the memory layer and themagnetization pinned layer.

FIG. 34 is a partly simplified enlarged perspective view of an ordinaryMRAM, with reading circuits omitted for brevity. This MRAM has ninememory cells and mutually intersecting bit lines 11 and writing wordlines 12. Each TMR element 10 is placed at the point of intersection.Writing into the TMR element 10 is accomplished by applying current tothe bit line 11 and the writing word line 12 simultaneously so that thetwo currents produce a combined magnetic field which changes thedirection of magnetization of the magnetic layer 2 of the TMR element 10parallel or antiparallel with respect to the magnetization pinned layer.

FIG. 35 is a schematic sectional view showing a memory cell which has afour-layered metal wiring. This memory cell is composed a reading n-typefield effect transistor 19, a writing word line 12, a TMR element 10,and a bit line 11, which are arranged one over another. The field effecttransistor 19 is composed of, for example, a p-type siliconsemiconductor substrate 13 and a p-type well region 14 formed thereon,in which are formed a gate insulating film 15, a gate electrode 16, asource region 17, and a drain region 18. To the source region 17 isconnected to a sense line through a source electrode 20. The fieldeffect transistor 19 functions as a switching element for reading. Thereading wiring 22 leading out between the word line 12 and the TMRelement 10 is connected to the drain region 18 through the contact plugs27 a to 27 c and the landing pads 28 a to 28 c in the insulating layers29 a to 29 g of laminate structure placed between the reading wiring 22and a drain electrode 23. Incidentally, the transistor 19 may be ann-type or p-type field effect transistor or any other switching elementsuch as diode, bipolar transistor, and MESFET (metal semiconductor fieldeffect transistor).

FIG. 36 is an equivalent circuit diagram of MRAM. It is assumed thatthis MRAM has six memory cells and mutually intersecting bit lines 11and writing word lines 12. At each point of intersection are arranged amemory element 10 and a field effect transistor 19 connected thereto.The field effect transistor 19 is connected also to a sense line 21 sothat it selects the element at the time of reading. The sense line 21 isconnected to a sense amplifier 21 b, so that stored information isdetected. There are also shown a bidirectioal current drive circuit 24for the writing word line and a current drive circuit 25 for the bitline.

FIG. 37 is an asteroid curve showing the writing condition for MRAM. Itrepresents the reversal threshold value in the direction ofmagnetization of the memory layer by the magnetic field H_(EA) appliedin the direction of easy axis and the magnetic field H_(HA) applied inthe direction of hard axis. The combined magnetic field vector outsidethe asteroid curve brings about the reversal of magnetic field. Bycontrast, the combined magnetic field vector within the asteroid curvedoes not reverse the cell from one bistable state into the other. Anycell which is not at the intersection of the word line and the bit linereceives the magnetic field generated individually by them, and it hasits direction of magnetization reversed if the magnitude of the magneticfield is larger than the one-direction reversal magnetic field H_(k).Consequently, only if the combined magnetic field is in the gray area,the selected cell permits selective writing.

As mentioned above, MRAM usually performs writing by means of twowriting lines (the bit line and the word line), which reverse themagnetic spin in a specified cell owing to the characteristics ofasteroid magnetization reversal. The combined magnetization in a singlememory region is determined by the vector synthesis of the magneticfield H_(EA) in the direction of easy axis and the magnetic field H_(HA)in the direction of hard axis, both applied to the memory region.Current flowing through the bit line applies to the cell the magneticfield H_(EA) in the direction of easy axis, and current flowing throughthe writing word line applies to the cell the magnetic field H_(HA) inthe direction of hard axis.

FIG. 38 illustrates the reading action by MRAM. Each TMR element 10 inMRAM is of layer structure as schematically shown. The magnetizationpinned layer (mentioned above) is represented by a single layer 26, andother layers are omitted except for the memory layer 2 and the tunnelbarrier layer 3.

As mentioned above, the writing of information is accomplished byapplying current to the bit lines 11 and word lines 12 which arearranged in a matrix pattern. Current applied to these lines produces acombined magnetic field at the point of their intersection, therebyreversing the magnetic spin of the cell. The direction of magnetic spinrepresents either “1” or “0” as information. The reading of informationis accomplished by using TMR effect resulting from magnetoresistanceeffect. TMR effect is a phenomenon that resistance varies depending onthe direction of magnetic spin. High resistance (with the magnetic spinantiparallel) represents “1” and low resistance (with the magnetic spinparallel) represents “0”. The reading of information is accomplished asfollows. Reading current (tunnel current) is applied across the wordline 12 and the bit line 11, and output in proportion to resistance isdetected by the sense line 21 through the field effect transistor 19 forreading.

In the case of MRAM consisting of one selecting element and one TMRelement as shown in FIG. 35, it is necessary to electrically insulatethe TMR element 10 by an insulating layer from the writing word line 12(referred to as word line for short hereinafter) which intersects withthe bit line 11. This makes it necessary to provide connecting holes forconnection between the reading wiring 22 and other wiring layers (loweror upper layers). Moreover, there should be a certain distance betweenthe word line 12 and the landing pad 28 c in the same layer. Therefore,the size of the memory cell of the MRAM cannot be equal to or smallerthan 8F2.

In other words, even though the TMR element 10 shown in FIG. 39 has anaspect ratio of 1:1 (A:B), the size of the memory cell of the MRAMcannot be equal to or smaller than 8F2 (or 2F×4F) in the direction ofthe bit line. (The aspect ratio of 1:1 means that the TMR element 10 isapproximately round and 3F is reduced to 2F in the direction in which itintersects with the bit line 11.) However, as mentioned later, it isnecessary that the shape of the TMR element 10 should be elongated inthe direction in which it intersects with the bit line 11. Therefore, itbecomes an ellipse with an aspect ratio of 1:2, as shown in FIG. 39.

As mentioned above, there has been proposed means to solve problems withMRAM of such structure that the lower layer wiring exists in the samelayer as the word line. (Refer to U.S. Pat. No. 5,940,319 (p. 5, column5, lines 45 to 56, and FIG. 10).) However, the proposed means forsolution is not necessarily satisfactory.

FIG. 39 is a schematic diagram showing a conventional MRAM (of 1T1Jtype) consisting of one selecting element and one TMR element. FIG. 39Ais a partial plan view, and FIG. 39B is a sectional view taken along theline b-b in FIG. 39A. As shown in FIG. 39B, the word line 12 iselectrically insulated from the TMR element 10 by an insulating layer(not shown). The TMR element 10, which is connected to the bit line 11,is connected to the landing pad 28, which is arranged on the same layeras the word line 12, through the reading wiring 22. This landing pad 28is further connected to the lower layer wiring 30 through the plug 27.

FIG. 39 shows the size of the memory cell of the MRAM. As FIG. 39A showsin plan, there should be a distance of F/2 between the boundary C ofadjacent memory cells and the landing pad 28, between the boundary C ofadjacent memory cells and the word line 12, and between the landing pad28 and the word line 12. Therefore, a length of 4F is necessary in thedirection along the bit line 11. On the other hand, a width of 3F isnecessary in the direction of intersection with the bit line 11. (Thewidth of 3F is a sum of the distance F/2 between the boundary C ofadjacent memory cells and the width (2F) of the bit line 11.) In actual,the TMR element 10 is formed elliptic, such that the aspect ratio A:B(where A is the minor axis of ellipse and B is the major axis ofellipse) is 1:2 from the standpoint of easy magnetization. Therefore,the length in the direction of intersection with the bit line 11 cannotbe made smaller than 3F.

In brief, the memory layer of the TMR element practically has itsdirection of energetically stable magnetic moment determined by itsshape anisotropy. Therefore, it is necessary that the aspect ratio ofthe TMR element pattern should be larger than 2 so that the reversal ofmagnetization takes place with a minimum of variation. The result isthat the cell size cannot be made smaller than 12F2, which is calculatedfrom (F+3F)×(2F+F), where F is the shorter side of TMR element and 2F isthe longer side of TMR element. In this case, a space of F/2 should beprovided between the side of the landing pad 28 and the word line andbetween the side of the landing pad 28 and the hole (not shown) forconnection of the reading wiring 22 to the lower layer wiring 30. (Thesecond space is equivalent to the width of the plug 27.) That is, thedistance between the word line 12 and the connecting hole should be F.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a magnetic memorydevice with a reduced cell size and a method for production thereof.

According to the present invention, there is provided a magnetic memorydevice including memory elements based on tunnel magnetoresistanceeffect elements, each consisting of a magnetization pinned layer inwhich the direction of magnetization is pinned, a tunnel barrier layer,and a magnetic layer in which the direction of magnetization isvariable, which are laid one over another, a first conducting layerformed on one side of the memory element with an insulating layerinterposed therebetween, and a second conducting layer formed on theother side of the memory element. Information is written into the memoryelement by applying current to a first conducting layer and also to asecond conducting layer. Written information is read out of the memoryelement through a reading wiring of the memory element which is attachedto the connecting hole formed in the insulating layer. The readingwiring is connected to a lower wiring existing below the firstconducting layer without passage through the conducting layer in thesame level as the first conducting layer. (The magnetic memory devicementioned above will be referred to as “the magnetic memory device ofthe present invention” hereinafter.)

According to the present invention, there is provided a method forproducing a magnetic memory device having memory elements based ontunnel magnetoresistance effect, each consisting of a magnetizationpinned layer in which the direction of magnetization is pinned, a tunnelbarrier layer, and a magnetic layer in which the direction ofmagnetization is variable, which are laid one over another, such thatinformation is written into the memory element as current is applied toa first conducting layer formed on one side of the memory element withan insulating layer interposed therebetween and also to a secondconducting layer formed on the other side of the memory element andwritten information is read out of the memory element through a readingwiring of the memory element which is attached to the connecting holeformed in the insulating layer. The method including a step of embeddinga lower wiring to be connected to the reading wiring in the firstinsulating layer formed below the first conducting layer, a step offorming the connecting hole through the second insulating layer in whichthe first conducting layer has been embedded, and a step of connectingthe reading wiring to the lower wiring through the connecting hole.

According to the present invention, the lower wiring to be connected tothe reading wiring is embedded in the first insulating layer below thefirst conducting layer and the reading wiring is connected to the lowerwiring through the connecting hole which is formed through the secondinsulating layer in which the first conducting layer has been embedded.The effect of this construction is that the space between the connectinghole and the first conducting layer can be reduced more than in the casewhere the lower wiring is formed in the same level as the firstconducting layer. This offers the advantage of reducing the size of thememory cell containing memory elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram showing the structure of the MRAMaccording to Embodiment 1 of the present invention. FIG. 1B is aschematic plan view of the MRAM according to Embodiment 1 of the presentinvention;

FIG. 2A to 2F is a diagram showing the process for production of MRAMaccording to Embodiment 1-1 of the present invention;

FIG. 3A to 3D is a diagram showing the process for production of MRAMaccording to Embodiment 1-1 of the present invention;

FIG. 4A to 4C is a diagram showing the process for production of MRAMaccording to Embodiment 1-1 of the present invention;

FIG. 5A to 5F is a diagram showing the process for production of MRAMaccording to Embodiment 1-2 of the present invention;

FIG. 6A to 6D is a diagram showing the process for production of MRAMaccording to Embodiment 1-2 of the present invention;

FIG. 7A to 7C is a diagram showing the process for production of MRAMaccording to Embodiment 1-2 of the present invention;

FIG. 8 is a schematic diagram showing the structure of the MRAMaccording to Embodiment 2 of the present invention;

FIG. 9A to 9F is a diagram showing the process for production of MRAMaccording to Embodiment 2-1 of the present invention;

FIG. 10A to 10E is a diagram showing the process for production of MRAMaccording to Embodiment 2-1 of the present invention;

FIG. 11A to 11D is a diagram showing the process for production of MRAMaccording to Embodiment 2-1 of the present invention;

FIG. 12A to 12F is a diagram showing the process for production of MRAMaccording to Embodiment 2-2 of the present invention;

FIG. 13A to 13E is a diagram showing the process for production of MRAMaccording to Embodiment 2-2 of the present invention;

FIG. 14A to 14D is a diagram showing the process for production of MRAMaccording to Embodiment 2-2 of the present invention;

FIG. 15 is a schematic diagram showing the structure of the MRAMaccording to Embodiment 3 of the present invention;

FIG. 16A to 16F is a diagram showing the process for production of MRAMaccording to Embodiment 3-1 of the present invention;

FIG. 17A to 17D is a diagram showing the process for production of MRAMaccording to Embodiment 3-1 of the present invention;

FIG. 18A to 18D is a diagram showing the process for production of MRAMaccording to Embodiment 3-1 of the present invention;

FIG. 19A to 19C is a diagram showing the process for production of MRAMaccording to Embodiment 3-1 of the present invention;

FIG. 20A to 20E is a diagram showing the process for production of MRAMaccording to Embodiment 3-2 of the present invention;

FIG. 21A to 21D is a diagram showing the process for production of MRAMaccording to Embodiment 3-2 of the present invention;

FIG. 22A to 22D is a diagram showing the process for production of MRAMaccording to Embodiment 3-2 of the present invention;

FIG. 23A to 23C is a diagram showing the process for production of MRAMaccording to Embodiment 3-2 of the present invention;

FIG. 24 is a schematic diagram showing the structure of the MRAMaccording to Embodiment 4 of the present invention;

FIG. 25A to 25F is a diagram showing the process for production of MRAMaccording to Embodiment 4-1 of the present invention;

FIG. 26A to 26E is a diagram showing the process for production of MRAMaccording to Embodiment 4-1 of the present invention;

FIG. 27A to 27D is a diagram showing the process for production of MRAMaccording to Embodiment 4-1 of the present invention;

FIG. 28A to 28D is a diagram showing the process for production of MRAMaccording to Embodiment 4-1 of the present invention;

FIG. 29A to 29F is a diagram showing the process for production of MRAMaccording to Embodiment 4-2 of the present invention;

FIG. 30A to 30D is a diagram showing the process for production of MRAMaccording to Embodiment 4-2 of the present invention;

FIG. 31A to 31D is a diagram showing the process for production of MRAMaccording to Embodiment 4-2 of the present invention;

FIG. 32A to 32D is a diagram showing the process for production of MRAMaccording to Embodiment 4-2 of the present invention;

FIG. 33 is a schematic perspective view of the TMR element of the MRAM;

FIG. 34 is a partial schematic perspective of the memory cell of theMRAM;

FIG. 35 is a schematic sectional view of the memory cell of the MRAM;

FIG. 36 is an equivalent circuit diagram of the MRAM;

FIG. 37 is a characteristic diagram showing the magnetic response at thetime of writing in the MRAM;

FIG. 38 is a diagram illustrating the principle for reading by the MRAM;

FIG. 39 is a schematic diagram showing a conventional MRAM consisting ofone selecting element and one TMR element. FIG. 39A is a plan view, andFIG. 39B is a sectional view taken along the line b-b in FIG. 39A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In their preferred embodiments of the magnetic memory device andproduction method of the present invention, the reading wiring should beextended to and connected to the conducting plug attached to theconnecting hole on the lower wiring.

Also, the reading wiring may be connected to the lower wiring by thelocal wiring connected to the side of the conducting layer below thetunnel barrier layer constituting the memory element.

In this case, the reading wiring should preferably be connected to thelower wiring through the connecting hole on the lower wiring.

Further, the plug should preferably be formed at the position as high asthe insulating layer or at the position lower than the first conductinglayer.

And, at least the side of the first conducting layer should be coveredwith a material having etch-selectivity for the insulating layer inwhich the first conducting layer has been embedded. This is desirablefor processing steps.

Also, the constituent layer above the magnetization pinned layer of thememory element is patterned, and at least the side of this pattern iscovered with a material having etch-selectivity for the lowerconstituent layer below the upper constituent layer and the insulatinglayer in which at least the first conducting layer has been embedded.This is desirable for processing steps.

The foregoing makes it possible to produce a desirable magnetic memorydevice which is constructed such that an insulating layer is formedbetween the magnetization pinned layer and the magnetic layer, the bitline and word line, which are formed above and below the memory element,induce a magnetic field upon current application to magnetize themagnetic layer in the prescribed direction, thereby writing information,and the written information is read by means of the tunnelmagnetoresistance effect through the insulating layer as the tunnelbarrier layer.

The preferred embodiments of the present invention will be describedbelow in more detail with reference to the accompanying drawings.

The embodiments described below are improved in connection between thereading wiring 22 and the lower layer wiring (not shown) over theconventional product shown in FIG. 39B, so as to reduce the size of thememory cell of MRAM. It is assumed that the TMR element has an aspectratio of 2. Writing variation decreases as the aspect ratio increases.The same symbols are used for the common parts in the drawings.

Embodiment 1

FIG. 1A is a schematic diagram showing the structure of the MRAMaccording to this embodiment. FIG. 1B is a schematic plan view of theMRAM according to this embodiment. As shown in these figures, the MRAMis constructed such that the landing pad does not exist at the samelevel as the word line 12, and the reading wiring 22 is connected to thelower layer wiring (not shown) through the connecting hole 42. Thisstructure makes it possible to bring the connecting hole 42 closer (byF/2) to the word line 12. In this way it is possible to decrease thesize in the direction along the bit line 11 to 3.5F.

Embodiment 1-1

The production process will be described with reference to FIGS. 2 to 4.In these figures, MOS transistors etc. under the lower layer wiring arenot shown. The same shall apply to other embodiments that follow.

On the lower layer wiring 31 (600 nm thick) are sequentially formed theHDP film 32 (800 nm thick) and the P-TEOS film 33 (1200 nm thick), asshown in FIG. 2A. The HDP film is a silicon oxide film formed byhigh-density plasma CVD. The P-TEOS film is a silicon oxide film formedfrom plasma tetraethyl orthosilicate by reduced pressure CVD. Then, CMP(chemical mechanical polishing) is performed such that an insulting film(700 nm thick) is left on the lower layer wiring 31, as shown in FIG.2B.

A connecting hole (not shown) for electrical connection to the lowerlayer wiring 31 is formed by lithography and etching. In this hole isdeposited a tungsten film by CVD. (This tungsten film is referred to asW-CVD hereinafter.) Finally, CMP is performed. In this way the W-plug 34is formed, as shown in FIG. 2C.

The P—SiN film (50 nm thick) and the P-TEOS film 35 (400 nm thick) aredeposited sequentially, as shown in FIG. 2D. The P—SiN film (not shown)is a silicon nitride film formed by plasma. It will be referred to asP—SiN hereinafter. Etching is performed on the P-TEOS film 35 through aphotoresist film (not shown) as a mask. Then etching is performed on theP—SiN film to form a wiring groove (not shown). In this groove aresequentially deposited Ta/TaN/Cu seed layers (not shown) by sputtering.The wiring groove is filled by Cu plating. The surface of the wiringgroove is planarized by CMP and the Cu wiring 12 (referred to as wordline hereinafter) is formed, as shown in FIG. 2E. The P—SiN film 37 (50nm thick) is deposited, as shown in FIG. 2F. Incidentally, filling ofthe wiring groove with Cu may also be accomplished by electrolessplating in place of electrolytic plating. The same shall apply to otherembodiments that follow.

Etching through the photoresist film 41 as the mask is performed to makethe connecting hole 42 which reaches the W-plug 34 formed on the lowerlayer wiring 31, as shown in FIG. 3A. In this way the lower layer wiring31 is formed below the word line 12, and there exists no other wiring atthe same level as the word line 12. Thus it is possible to form theconnecting hole 42 easily by full-wafer etching closer to the word line12 by F/2.

PVD (physical vapor deposition) is performed to form sequentially thebarrier layer 51, the antiferromagnetic layer 52, the ferromagneticlayer 53, the tunnel insulating layer 54, the ferromagnetic layer(memory layer) 55, and the cap layer 56, as shown in FIG. 3B. In thefollowing figures, the barrier layer 51, the antiferromagnetic layer 52,and the ferromagnetic layer 53 may be collectively referred to as thepinned layer 60, and the memory layer 55 and the cap layer 56 may becollectively referred to as the free layer 50. The same shall apply toother embodiments that follow.

The barrier layer 51 is formed from titanium nitride, tantalum, ortantalum nitride. The antiferromagnetic layer 52 is formed fromiron-manganese, nickel-manganese, platinum-manganese, oriridium-manganese. The ferromagnetic layer 53 is formed from nickel-ironand/or cobalt alloy. The lower ferromagnetic layer 53 has its directionof magnetization spinned by exchange coupling with the underlyingantiferromagnetic layer 52. The tunnel insulating layer 54 is usuallyformed from alumina Al₂O₃. It is so thin (0.5 to 5 nm) that it is formedby ALD (atomic layer deposition) method or it is deposited by sputteringwith aluminum and subsequent plasma oxidation. The upper ferromagneticlayer 55 is formed also from nickel-iron and/or cobalt alloy. This layerhas its direction of magnetization changed parallel or antiparallel withrespect to the underlying ferromagnetic layer by the externally appliedmagnetic field. The cap layer 56 is formed from the same material asused for the barrier layer. The same shall apply to other embodimentsthat follow.

The P-TEOS film 38 (200 nm thick) is deposited, and then it is patternedby reactive ion etching technique through the photoresist film 43(formed thereon) as the mask, as shown in FIG. 3C.

With the photoresist film removed, reactive ion etching is performed onthe cap layer 56 and the upper ferromagnetic layer 55 through the P-TEOSfilm 38 as the mask, as shown in FIG. 3D. This etching should completelyremove the upper ferromagnetic layer 55 and then terminates in thetunnel insulating film 54. Also, this etching should be carried out suchthat the P-TEOS film 38 (thicker than 100 nm) remains on the cap layer56 and the memory layer 55. The etching gas is a halogen gas containingchlorine or a carbon monoxide gas mixed with NH₃.

Etching is performed through the photoresist film 44 and the P-TEOS film38 as the mask to remove the remainder of the tunnel insulating film 54and the pinned layer 60 (which consists of the lower ferromagnetic layer53, the underlying antiferromagnetic layer 52, and the barrier layer51), thereby forming the wiring pattern connecting to the magnetizationpinned layer and the underlying layer, as shown in FIG. 4A. In this waythe reading wiring 22 is formed which extends in the connecting hole.

CVD or PVD is performed to deposit the insulating film 45 of SiO₂ orAl₂O₃ over the entire surface, as shown in FIG. 4B. CMP is performed toplanarize the insulating film 45 and the P-TEOS film 38, so that the caplayer 56 (which is the uppermost layer of the TMR) is exposed. Theexposed part functions as a self-aligned contact for the bit line.

The bit line 11, the peripheral circuit wiring (not shown), and thebonding pad region (not shown) are formed by the standard wiringtechnology, as shown in FIG. 4C. The plasma silicon nitride film 46 isdeposited over the entire surface. Finally, a hole for the bonding padregion is made. Thus, the wafer process for LSI (large scaleintegration) is completed.

Embodiment 1-2

The production process will be described with reference to FIGS. 5 to 7.

First, a lower layer metal wiring 31 (600 nm) is formed. On this layerare sequentially deposited the HDP film 32 (800 nm thick) and the P-TEOSfilm 33 (1200 nm thick), as shown in FIG. 5A. CMP is performed such thatan insulting film (700 nm thick) is left on the lower layer wiring 31,as shown in FIG. 5B.

The P—SiN film (50 nm thick) (not shown) and the P-TEOS film 35 (400 nmthick) are sequentially deposited, as shown in FIG. 5C. Etching isperformed on the P-TEOS film 35 and the P—SiN film through a photoresistfilm (not shown) as the mask, so that a wiring groove is formed. In thiswiring groove are sequentially deposited Ta/TaN/Cu seed layers bysputtering (not shown). The wiring groove is filled with Cu plating. Thesurface of the wiring groove is planarized by CMP, and the word line 12is formed, as shown in FIG. 5D. The P—SiN film 37 (50 nm thick) isdeposited, as shown in FIG. 5E.

Etching is performed through the photoresist film 41 as the mask so asto make the connecting hole 42 reaching the lower layer wiring 31, asshown in FIG. 5F. In this way, the lower layer wiring 31 is formed belowthe word line 12. Therefore, there exist no other wiring at the samelevel as the word line 12 and the connecting hole 42 can be made closerto the word line 12 by F/2. Moreover, in this way they can be formed allat once by etching.

With the W-plug 40 embedded in the connecting hole 42, as shown in FIG.6A, PVD is performed to deposit the pinned layer 60 and the free layer50 with the same materials as used in Embodiment 1-1, as shown in FIG.6B. The pinned layer 60 consists of the barrier layer 51, theantiferromagnetic layer 52, and the ferromagnetic layer 53. The freelayer 50 consists of the tunnel insulating film 54, the ferromagneticlayer (memory layer) 55, and the cap layer 56. In this way it ispossible to reduce the distance between the word line 12 and the plug 40for connection to the reading wiring 22 (mentioned later).

The P-TEOS film 38 (200 nm thick) is deposited, and then it is patternedby reactive ion etching through the photoresist film 43 as the mask, asshown in FIG. 6C.

With photoresist film removed, reactive ion etching is performed on thefree layer 50 (consisting of the cap layer 56 and the upperferromagnetic layer 55) through the P-TEOS film 38 as the mask, as shownin FIG. 6D. Etching should be so carried out as to remove the upperferromagnetic layer 55 completely and then terminates in the tunnelinsulating film 54. In addition, etching should be so carried out toleave the P-TEOS film 38 (thicker than 100 nm) on the cap layer 56 andthe memory layer 55. The etching gas may be a halogen gas containingchlorine or carbon monoxide mixed with NH₃.

Etching is performed on the remainder of the tunnel insulating film 54and the pinned layer 60 (consisting of the lower ferromagnetic layer 53,the underlying antiferromagnetic layer 52, and the barrier layer 51)through the photoresist 44 and the P-TEOS 38 as the mask, as shown inFIG. 7A, so that the wiring pattern that connects to the magnetizationpinned layer and the underlying layer is formed.

The insulating film 45 of SiO₂ or Al₂O₃ is deposited by CVD or PVD overthe entire surface as shown in FIG. 7B. CMP is performed to planarizethe insulating film 45 and the P-TEOS film 38, so that the cap layer 56(the uppermost layer of the TMR) is exposed. The exposed part functionsas a self-aligned contact for the bit line.

The bit line 11, the peripheral circuit wiring (not shown), and thebonding pad region (not shown) are formed by the standard wiringtechnology, as shown in FIG. 7C. The plasma silicon nitride film 46 isdeposited over the entire surface. Finally, a hole for the bonding padregion is made. Thus, the wafer process for LSI is completed.

The embodiments 1-1 and 1-2 mentioned above offer the followingadvantages. The reading wiring 22 (shown in FIG. 1) is connected to thelower layer wiring (not shown) by means of the plug 34 (in Embodiment1-1) or the plug 40 (in Embodiment 1-2). The plug 34 is formed on thelower layer wiring 31 which is arranged below the word line 12, and thereading wiring 22 is extended into the connecting hole for itsconnection. The plug 40 is formed in the entire connecting hole reachingthe lower layer wiring 31. The arrangement in this manner eliminates theconventional landing pad at the same level as the word line 12;therefore, the connecting hole 42 can be formed close to the word line12 and the space between the word line 12 and the plug 40 or the readingwiring 22 extending into the connecting hole 42 can be reduced by F/2 ascompared with the conventional one shown in FIG. 39. Thus the cell sizeequal to or smaller than 12F2 can be realized.

According to the conventional structure (shown in FIG. 39), the cellsize needs 12F2, because the space in the direction along the bit line11 needs 4F and the space in the direction intersecting with the bitline 11 needs 3F. (F denotes half the pitch of the design rule.) Thesize of 4F in the direction along the bit line 11 is necessary toaccommodate the writing word line and the landing pad for connection tothe underlying layer in the same wiring layer.

By contrast, the structure in the embodiments mentioned above has nolanding pads, so that connection is made directly to the lower layerwiring 31 through the plug. This structure only needs a space of F/2 tosecure breakdown voltage and to provide an allowance for overlapping ofthe word line 12 and the plug. Assuming a design rule of 0.18 μm, F willbe 0.27 μm. If 0.12 μm is assumed for the allowance for breakdownvoltage and overlapping, then 0.12 μm is equal to or smaller than 0.5F(0.12/0.27=0.44<0.5). This means that the space in the direction alongthe bit line is reduced by 0.5F to 3.5F. Thus, the size of the memorycell will be 10.5F2 (3.5F in the direction along the bit line×3F in thedirection intersecting with the bit line). This size is smaller thanthat of the conventional structure shown in FIG. 39.

Embodiment 2

FIG. 8 is a schematic diagram showing the structure of the MRAMaccording to this embodiment. As in the case of Embodiment 1, the MRAMis constructed such that the landing pad does not exist at the samelevel as the word line 12, and the reading wiring 22 is connected to thelower layer wiring (not shown) through the connecting hole 42. If theupper and lateral surfaces of the word line are covered with abreakdown-resistant material with etching selectivity, this structurepermits the space between the word line 12 and the connecting hole 42 tobe reduced more than that in Embodiment 1. In fact, the structure inEmbodiment 2 has the MRAM size reduced to 3.2F (corresponding to 4F inFIG. 39) in the direction along the bit line 11.

Embodiment 2-1

The production process will be described with reference to FIGS. 9 to11.

On the lower layer wiring 31 (600 nm thick) are sequentially formed theHDP film 32 (800 nm thick) and the P-TEOS film 33 (1200 nm thick), asshown in FIG. 9A. Then, CMP is performed such that an insulting film(700 nm thick) is left on the lower layer wiring 31, as shown in FIG.9B.

A connecting hole (not shown) for electrical connection to the lowerlayer wiring 31 is formed by lithography and etching. In this hole isformed the W-plug 34 by W-CVD and ensuing CMP, as shown in FIG. 9C.

The multi-layer film 36 (such as Ti/TiN/Al-0.5% Cu=10/30/700 nm) isdeposited by sputtering, and then the P—SiN film 37 (100 nm thick) isdeposited, as shown in FIG. 9D. Etching through the photoresist film 41as the mask is performed on the P—SiN film 37 and the metal multi-layerfilm 36 in order to form the word line 12, as shown in FIG. 9E.

The P—SiN film 47 (50 nm thick) is deposited and etch-back is performedon it, as shown in FIG. 9F. This step forms the side wall 47 of P—SiN onthe lateral surface of the word line 12, as shown in FIG. 10A. Theamount of overetching should be set up so that the P—SiN film 37 remainsequal to or more than 70 nm on the word line 12.

CVD or PVD is performed to deposit the insulating film 45 of SiO₂ orAl₂O₃ over the entire surface, and CMP is performed to planarize theinsulating film 45, so that the P—SiN film 37 is exposed, as shown inFIG. 10B.

Etching through the photoresist film 41 as the mask is performed to makethe connecting hole 42 which reaches the W-plug 34 formed on the lowerlayer wiring 31, as shown in FIG. 10C. This etching should be carriedout with high selectivity for the interlayer insulating film 45 and theP—SiN film 37 and the side wall 47 (formed on the upper and lateralsurfaces of the word line 12, respectively). In this way the lower layerwiring 31 is formed below the word line 12, and it is possible to reducemore the distance between the word line 12 and the connecting hole 42for connection to the plug 34 formed above it. Moreover, it can beeasily formed by full-wafer etching.

With the resist mask 41 removed, PVD is carried out to sequentially formthe pinned layer 60 (consisting of the barrier layer 51, theantiferromagnetic layer 52, and the ferromagnetic layer 53) and the freelayer 50 (consisting of the tunnel insulating film 54, the ferromagneticlayer (memory layer) 55, and the cap layer 56) from the same materialsas used in Embodiment 1-1, as shown in FIG. 10D.

The P-TEOS film 38 (200 nm thick) is deposited and then it is patternedby reactive ion etching through the photoresist film 43 as the mask, asshown in FIG. 10E.

With the photoresist film removed, reactive ion etching is performed onthe free layer 50 (consisting of the cap layer 56 and the upperferromagnetic layer 55) through the P-TEOS film 38 as the mask, as shownin FIG. 11A. Etching should be carried out such that it terminates inthe tunnel insulating film 54 after it has completely removed the upperferromagnetic layer 55. In addition, etching should be carried out suchthat the P-TEOS film 38 remains more than 100 nm on the cap layer 56 andthe memory layer 55. The etching gas is a halogen gas containingchlorine or a carbon monoxide gas mixed with NH₃.

Etching is performed through the photoresist film 44 and the P-TEOS film38 as the mask to remove the remainder of the tunnel insulating film 54and the pinned layer 60 (which consists of the lower ferromagnetic layer53, the underlying antiferromagnetic layer 52, and the barrier layer51), thereby forming the wiring pattern connecting to the magnetizationpinned layer and the underlying layer, as shown in FIG. 11B. In this waythe reading wiring 22 is formed which extends in the connecting hole.

CVD or PVD is performed to deposit the insulating film 48 of SiO₂ orAl₂O₃ over the entire surface, as shown in FIG. 11C. CMP is performed toplanarize the insulating film 48 and the P-TEOS film 38, so that the caplayer 56 (which is the uppermost layer of the TMR) is exposed. Theexposed part functions as a self-aligned contact for the bit line.

The bit line 11, the peripheral circuit wiring (not shown), and thebonding pad region (not shown) are formed by the standard wiringtechnology, as shown in FIG. 11D. The plasma silicon nitride film 46 isdeposited over the entire surface. Finally, a hole for the bonding padregion is made. Thus, the wafer process for LSI is completed.

Embodiment 2-2

The production process will be described with reference to FIGS. 12 to14.

On the lower layer wiring 31 (600 nm thick) are sequentially formed theHDP film 32 (800 nm thick) and the P-TEOS film 33 (1200 nm thick), asshown in FIG. 12A. Then, CMP is performed such that an insulting film(700 nm thick) is left on the lower layer wiring 31, as shown in FIG.12B.

The metal multi-layer film 36 (such as Ti/TiN/Al-0.5% Cu=10/30/700 nm)is deposited by sputtering, and then the P—SiN film 37 (100 nm thick) isdeposited, as shown in FIG. 12C. Etching though the photoresist film 41as the mask is performed on the P—SiN film 37 and the metal multi-layerfilm 36 in order to form the word line 12, as shown in FIG. 12D.

The P—SiN film 47 (50 nm thick) is deposited and etch-back is performedon it, as shown in FIG. 12E. This step forms the side wall 47 of P—SiNon the lateral surface of the word line 12, as shown in FIG. 12F. Theamount of overetching should be set up so that the P—SiN film 37 remainsmore than 70 nm on the word line 12.

CVD or PVD is performed to deposit the insulating film 45 of SiO₂ orAl₂O₃ over the entire surface, and CMP is performed to planarize theinsulating film 45, so that the P—SiN film 37 is exposed, as shown inFIG. 13A.

Etching through the photoresist film 41 as the mask is performed to makethe connecting hole 42 which reaches the previously formed lower layerwiring 31, as shown in FIG. 13B. This etching should be carried out withhigh selectivity for the interlayer insulating film 45 and the P—SiNfilm 37 and the side wall 47 (formed on the upper and lateral surfacesof the word line 12, respectively). In this way the lower layer wiring31 is formed below the word line 12; therefore, there exist no otherwirings at the same level as the word line 12. Thus, it is possible tobring the connecting hole 42 closer to the word line 12. Moreover, itcan be easily formed by full-wafer etching.

With the W-plug 40 embedded in the connecting hole 42, as shown in FIG.13C, PVD is carried out to sequentially deposit the pinned layer 60(consisting of the barrier layer 51, the antiferromagnetic layer 52, andthe ferromagnetic layer 53) and the free layer 50 (consisting of thetunnel insulating film 54, the ferromagnetic layer (memory layer) 55,and the cap layer 56) from the same materials as used in Embodiment 1-1,as shown in FIG. 13D. In this way it is possible to reduce the distancebetween the word line 12 and the plug 40 for connection with the readingwiring 22 mentioned later.

The P-TEOS film 38 (200 nm thick) is deposited and then it is patternedby reactive ion etching through the photoresist film 43 as the mask, asshown in FIG. 13E.

With the photoresist film removed, reactive ion etching is performed onthe free layer 50 (consisting of the cap layer 56 and the upperferromagnetic layer 55) through the P-TEOS film 38 as the mask, as shownin FIG. 14A. Etching should be carried out such that it terminates inthe tunnel insulating film 54 after it has completely removed the upperferromagnetic layer 55. In addition, etching should be carried out suchthat the P-TEOS film 38 remains more than 100 nm on the cap layer 56.The etching gas is a halogen gas containing chlorine or a carbonmonoxide gas mixed with NH₃.

Etching is performed through the photoresist film 44 and the P-TEOS film38 as the mask to remove the remainder of the tunnel insulating film 54and the pinned layer 60 (which consists of the lower ferromagnetic layer53, the underlying antiferromagnetic layer 52, and the barrier layer51), thereby forming the wiring pattern connecting to the magnetizationpinned layer and the underlying layer, as shown in FIG. 14B.

CVD or PVD is performed to deposit the insulating film 48 of SiO₂ orAl₂O₃ over the entire surface, as shown in FIG. 14C. CMP is performed toplanarize the insulating film 48 and the P-TEOS film 38, so that the caplayer 56 (which is the uppermost layer of the TMR) is exposed. Theexposed part functions as a self-aligned contact for the bit line.

The bit line 11, the peripheral circuit wiring (not shown), and thebonding pad region (not shown) are formed by the standard wiringtechnology, as shown in FIG. 14D. The plasma silicon nitride film 46 isdeposited over the entire surface. Finally, a hole for the bonding padregion is made. Thus, the wafer process for LSI is completed.

Embodiments 2-1 and 2-2 mentioned above offer the following advantages.The lower layer wiring 31 is formed below the word line 12. The uppersurface 37 and the lateral surface 47 of the word line 12 are coveredwith an etch-selective material. The connecting hole 42 is formed forconnection to the plug 34 formed on the lower layer wiring 31. Thereading wiring 22 extends in the connecting hole 42 for directconnection to the plug 34 (in Embodiment 2-1), or the plug 40 is formedin the entire connecting hole reaching the lower layer wiring 31 and thereading wiring 22 is connected to this plug 40 (in Embodiment 2-2).Therefore, the upper and lateral surfaces of the word line 12 arecovered with an etch-selective material. In either case, the word line12 is protected with an etch-selective material when the connecting hole42 is formed.

Consequently, there is no possibility that the word line 12 is damagedwhen the connecting hole 42 is formed. This permits the connecting hole40 to be easily formed close to the word line 12. Thus, it is possibleto reduce the distance between the word line 12 and the plug 40 or thereading wiring 22 formed in the connecting hole 42 more than inEmbodiment 1 by extending the reading wiring 22 to the connecting hole42 or by connecting it to the lower wiring 31 through the plug. Thespace between the word line 12 and the connecting hole 42 shown in FIG.1B can be reduced to F/2 or less and the size in the direction along thebit line 11 can be reduced to 3.2F.

In other words, the structure according to Embodiment 2 differs fromthat according to Embodiment 1 in that the difference between the wordline 12 and the plug 34 or 40 for connection to the reading wiring 22 isreduced more, because the word line 12 one layer below the TMR element10 is covered with the P—SiN film or Al₂O₃ film having a high breakdownvoltage and a high etch-selectivity for the commonly used silicon oxideinterlayer film. Assuming a design rule of 0.18 μm, F will be 0.27 μm.There is no need for allowance to ensure the breakdown voltage, but itis only necessary to set aside 0.2F for overlapping allowance.Therefore, the length in the direction along the bit line is 3.2F (whichcorresponds to 4F in FIG. 39). It follows that the size of the memorycell is 9.6F2 (3.2F×3F in the direction intersecting with the bit line.)

Embodiment 3

FIG. 15 is a schematic diagram showing the structure of the MRAMaccording to this embodiment. As in the case of Embodiments 1 and 2, theMRAM is constructed such that the landing pad does not exist at the samelevel as the word line 12, and the reading wiring is connected to thelower layer wiring 31 through the local wiring 22A connected to theconducting layer 70 under the TMR element 10. Since the local wiring 22Aneeds only a small area, the distance corresponding to that indicated by4F in FIG. 39 is reduced to 3.5F, as in the case of Embodiment 1.

Embodiment 3-1

The production process will be described with reference to FIGS. 16 to19.

On the lower layer wiring 31 (600 nm thick) are sequentially depositedthe HDP film 32 (800 nm thick) and the P-TEOS film 33 (1200 nm thick),as shown in FIG. 16A. Then, CMP is performed such that an insulting film(700 nm thick) is left on the lower layer wiring 31, as shown in FIG.16B.

A connecting hole (not shown) for electrical connection to the lowerlayer wiring 31 is formed by lithography and etching. In this hole isformed the W-plug 34 by W-CVD and ensuing CMP, as shown in FIG. 16C.

The P—SiN film (50 nm thick) (not shown) and the P-TEOS film 35 (400 nmthick) are deposited sequentially, as shown in FIG. 16D. Etching throughthe photoresist film (not shown) as the mask is performed on the P-TEOSfilm 35 and then etching is performed on the P—SiN film to form thewiring groove (not shown). In this wiring groove are sequentiallydeposited the Ta/TaN/Cu seed layers (not shown) by sputtering. Thewiring groove is filled by Cu plating. CMP is performed to planarize thesurface of the wiring groove to form the word line 12, as shown in FIG.16E. The P—SiN film 37 (50 nm thick) is deposited, as shown in FIG. 16F.In this way the lower layer wiring 31 is formed at the lower level thanthe word line 12.

PVD is carried out to sequentially form the pinned layer 60 (consistingof the barrier layer 51, the antiferromagnetic layer 52, and theferromagnetic layer 53) and the free layer 50 (consisting of the tunnelinsulating film 54, the ferromagnetic layer (memory layer) 55, and thecap layer 56) from the same materials as used in Embodiment 1, as shownin FIG. 17A.

The P-TEOS film 38 (200 nm thick) is deposited and then it is patternedby reactive ion etching through the photoresist film 43 as the mask, asshown in FIG. 17B. This P-TEOS film 38 functions as the etch-selectivefilm that covers the upper surface of the TMR element.

With the photoresist film removed, reactive ion etching is performed onthe free layer 50 (consisting of the cap layer 56 and the upperferromagnetic layer 55) through the P-TEOS film 38 as the mask, as shownin FIG. 17C. Etching should be carried out such that it terminates inthe tunnel insulating film 54 after it has completely removed the upperferromagnetic layer 55. In addition, etching should be carried out suchthat the P-TEOS film 38 remains more than 100 nm on the cap layer 56 andthe memory layer 55. The etching gas is a halogen gas containingchlorine or a carbon monoxide gas mixed with NH₃.

The P-TEOS film 39 (200 nm thick) is deposited over the entire uppersurface, as shown in FIG. 17D. Etch-back is performed on it to form theside wall 47 as the etching mask on the lateral surface of the freelayer 50, as shown in FIG. 18A.

The tunnel insulating film 54 and the pinned layer 60 are removed byreactive ion etching that employs as the mask the upper P-TEOS film 38covering the free layer 50 and the side wall 39 of P-TEOS, as shown inFIG. 18B. The etching gas is a halogen gas containing chlorine or acarbon monoxide gas mixed with NH₃.

The photoresist mask 41 is formed and the connecting hole 42 reachingthe plug 34 is formed, as shown in FIG. 18C. The photoresist mask 41 isformed such that the P-TEOS film 38 and the side wall 39 are partlyexposed. The P—SiN film 37 and the P-TEOS film 35 which are covered bythe P-TEOS film 38 and the side wall 39 remain unetched. In this way theword line 12 is completely protected and the connecting hole 42 isformed close to the word line 12. Moreover, it can be easily formed byfull-wafer etching.

With the resist mask 41 removed, the Cu film 49 is formed by sputteringover the entire upper surface, as shown in FIG. 18D. Etch-back isperformed on the Cu film 49 so as to remove the upper Cu film, as shownin FIG. 19A. The tunnel insulating film 54, the lateral surface of thepinned layer 60, and the side wall surface of the connecting hole 42remain. The local wiring 22A is formed from the Cu film which hasremained, extending from the tunnel insulating film 54 and the one sideof the pinned layer 60 to one of the side wall surfaces of theconnecting hole 42. The distance between the word line 12 and the localwiring 22A can be reduced.

CVD or PVD is performed to deposit the insulating film 45 of SiO₂ orAl₂O₃ over the entire surface, and CMP is performed to planarize andpolish the insulating film 45 and the P-TEOS film 38, so that the caplayer 56 (which is the uppermost layer of the TMR) is exposed, as shownin FIG. 19B. The exposed part functions as a self-aligned contact forthe bit line.

The bit line 11, the peripheral circuit wiring (not shown), and thebonding pad region (not shown) are formed by the standard wiringtechnology, as shown in FIG. 19C. The plasma silicon nitride film 46 isdeposited over the entire surface. Finally, a hole for the bonding padregion is made. Thus, the wafer process for LSI is completed.

Embodiment 3-2

The production process will be described with reference to FIGS. 20 to23.

On the lower layer metal wiring 31 (600 nm thick) are sequentiallydeposited the HDP film 32 (800 nm thick) and the P-TEOS film 33 (1200 nmthick), as shown in FIG. 20A. Then, CMP is performed such that aninsulting film (700 nm thick) is left on the metal wiring 31, as shownin FIG. 20B.

The P—SiN film (50 nm thick) (not shown) and the P-TEOS film 35 (400 nmthick) are deposited sequentially, as shown in FIG. 20C. Etching throughthe photoresist film (not shown) as the mask is performed on the P-TEOS35 and then etching is performed on the P—SiN film to form the wiringgroove (not shown). In this wiring groove are sequentially deposited theTa/TaN/Cu seed layers (not shown) by sputtering. The wiring groove isfilled by Cu plating. CMP is performed to planarize the surface of thewiring groove to form the word line 12, as shown in FIG. 20D. The P—SiNfilm 37 (50 nm thick) is deposited, as shown in FIG. 20E. In this waythe lower layer wiring 31 is formed at the lower level than the wordline 12.

PVD is carried out to sequentially form the pinned layer 60 (consistingof the barrier layer 51, the antiferromagnetic layer 52, and theferromagnetic layer 53) and the free layer 50 (consisting of the tunnelinsulating film 54, the ferromagnetic layer (memory layer) 55, and thecap layer 56) from the same materials as used in Embodiment 1, as shownin FIG. 21A.

The P-TEOS film 38 (200 nm thick) is deposited and then it is patternedby reactive ion etching through the photoresist film 43 as the mask, asshown in FIG. 21B. This P-TEOS film 38 functions as the etch-selectivefilm that covers the upper surface of the TMR element.

With the photoresist film removed, reactive ion etching is performed onthe free layer 50 (consisting of the cap layer 56 and the upperferromagnetic layer 55) through the P-TEOS film 38 as the mask, as shownin FIG. 21C. Etching should be carried out such that it terminates inthe tunnel insulating film 54 after it has completely removed the upperferromagnetic layer 55. In addition, etching should be carried out suchthat the P-TEOS film 38 remains more than 100 nm on the cap layer 56 andthe memory layer 55. The etching gas is a halogen gas containingchlorine or a carbon monoxide gas mixed with NH₃.

The P-TEOS film 39 (200 nm thick) is deposited over the entire uppersurface, as shown in FIG. 21D. Etch-back is performed on it to form theside wall 47 (as the etching mask) on the lateral surface of the freelayer 50, as shown in FIG. 22A.

The tunnel insulating film 54 and the pinned layer 60 are removed byreactive ion etching that employs as the mask the upper P-TEOS film 38covering the free layer 50 and the side wall 39 of P-TEOS, as shown inFIG. 22B. The etching gas is a halogen gas containing chlorine or acarbon monoxide gas mixed with NH₃.

The photoresist mask 41 is formed and the connecting hole 42 reachingthe lower wiring 31 is formed, as shown in FIG. 22C. The photoresistmask 41 is formed such that the P-TEOS film 38 and the side wall 39 arepartly exposed. The P—SiN film 37 and the P-TEOS film 35 which arecovered by the P-TEOS film 38 and the side wall 39 remain unetched. Inthis way the word line 12 is completely protected and the connectinghole 42 is formed close to the word line 12. Moreover, it can be easilyformed by full-wafer etching.

With the resist mask 41 removed, the Cu film 49 is formed by sputteringover the entire upper surface, as shown in FIG. 22D. Etch-back isperformed on the Cu film 49 so as to remove the upper Cu film, as shownin FIG. 23A. The Cu film remains on the tunnel insulating film 54, thelateral surface of the pinned layer 60, and the side wall surface of theconnecting hole 42. The local wiring 22A is formed from the Cu filmwhich has remained, extending from the tunnel insulating film 54 and theone side of the pinned layer 60 to one of the side wall surfaces of theconnecting hole 42. The distance between the word line 12 and the localwiring 22A can be reduced.

CVD or PVD is performed to deposit the insulating film 45 of SiO₂ orAl₂O₃ over the entire surface, and CMP is performed to planarize andpolish the insulating film 45 and the P-TEOS film 38, so that the caplayer 56 (which is the uppermost layer of the TMR) is exposed, as shownin FIG. 23B. The exposed part functions as a self-aligned contact forthe bit line.

The bit line 11, the peripheral circuit wiring (not shown), and thebonding pad region (not shown) are formed by the standard wiringtechnology, as shown in FIG. 23C. The plasma silicon nitride film 46 isdeposited over the entire surface. Finally, a hole for the bonding padregion is made. Thus, the wafer process for LSI is completed.

Embodiment 3 mentioned above offers the following advantages. The lowerlayer wiring 31 is formed below the word line 12. The upper surface 38and the lateral surface 39 of the free layer 50 of the TMR element 10covered with a mask of etch-selective material. By using this mask andthe resist mask 41 as the mask, the connecting hole 42 for connection tothe plug 34 formed on the lower layer wiring 31 is formed (in Embodiment3-1) or the connecting hole 42 reaching the lower layer wiring 31 isformed (in Embodiment 3-2). The reading wiring is formed with the localwiring 22A extending from the tunnel insulating film 54 and the lateralsurface of the pinned layer 60 to the side wall surface of theconnecting hole 42, and it is connected to the lower layer wiring 31directly or through the plug 34.

However, since the upper surface and the lateral surface of the freelayer 50 of the TMR element 10 are covered with an etch-selective mask,it is possible to surely protect the word line 12 existing below thismask when the connecting hole 42 is formed, and the connecting hole 42can be easily formed close to the word line 12. Therefore, it ispossible to easily form the memory cell in which the distance betweenthe word line 12 and the local wiring 22A is reduced as in Embodiment 1.

As the result, the MRAM region in the direction along the bit line canbe reduced, by 0.5F, to 3.5F (4F−0.5F) as in Embodiment 1, and thememory size can be reduced to 10.5F2 (3.5F in the direction along thebit line×3F in the direction intersecting with the bit line). Thisresult should be compared with the MRAM of conventional structure inwhich the region in the direction along the bit line is 4F, as shown inFIG. 39.

Embodiment 4

FIG. 24 is a schematic diagram showing the structure of the MRAMaccording to this embodiment. As in the case of the above-mentionedembodiments, the MRAM is constructed such that the landing pad does notexist at the same level as the word line 12, and the reading wiring isconnected to the lower layer wiring 31 through the local wiring 22Aconnected to the conducting layer 70 under the TMR element 10. Moreover,the MRAM is constructed such that the upper and lateral surfaces of theword line 12 are covered with an etch-selective material, so that theconnecting hole 42 is formed closer to the word line 12. Thus, thedistance between the word line 12 and the local wiring 22A is reducedfurther and the size of the MRAM in the direction along the bit line isreduced to 3F (which corresponds to 4F in FIG. 39).

Embodiment 4-1

The production process will be described with reference to FIGS. 25 to28.

On the lower layer wiring 31 (600 nm thick) are sequentially depositedthe HDP film 32 (800 nm thick) and the P-TEOS film 33 (1200 nm thick),as shown in FIG. 25A. Then, CMP is performed such that an insulting film(700 nm thick) is left on the lower layer wiring 31, as shown in FIG.25B.

A connecting hole (not shown) for electrical connection to the lowerlayer wiring 31 is formed by lithography and etching. In this hole isformed the W-plug 34 by W-CVD and ensuing CMP, as shown in FIG. 25C.

The metal multi-layer film 36 (such as Ti/TiN/Al-0.5% Cu=10/30/700 nm)is deposited by sputtering, and then the P—SiN film 37 (100 nm thick) isdeposited, as shown in FIG. 25D. Etching though the photoresist film 41as the mask is performed on the P—SiN film 37 and the metal multi-layerfilm 36 in order to form the word line 12, as shown in FIG. 25E. In thisway, the lower layer wiring 31 is formed below the word line 12.

The P—SiN film 47 (50 nm thick) is deposited and etch-back is performedon it, as shown in FIG. 25F. This step forms the side wall 47 of P—SiNon the lateral surface of the word line 12, as shown in FIG. 26A. Theamount of overetching should be set up so that the P—SiN film 37 remainsmore than 70 nm on the word line 12.

CVD or PVD is performed to deposit the insulating film 45 of SiO₂ orAl₂O₃ over the entire surface, and CMP is performed to planarize andpolish the insulating film 45, so that P—SiN film 37 is exposed, asshown in FIG. 26B.

PVD is carried out to sequentially form the pinned layer 60 (consistingof the barrier layer 51, the antiferromagnetic layer 52, and theferromagnetic layer 53) and the free layer 50 (consisting of the tunnelinsulating film 54, the ferromagnetic layer (memory layer) 55, and thecap layer 56) from the same materials as used in Embodiment 1, as shownin FIG. 26C.

The P-TEOS film 38 (200 nm thick) is deposited and then it is patternedby reactive ion etching through the photoresist film 43 as the mask, asshown in FIG. 26D. This P-TEOS film 38 functions as the etch-selectivefilm that covers the upper surface of the TMR element.

With the photoresist film removed, reactive ion etching is performed onthe free layer 50 (consisting of the cap layer 56 and the upperferromagnetic layer 55) through the P-TEOS film 38 as the mask, as shownin FIG. 26E. Etching should be carried out such that it terminates inthe tunnel insulating film 54 after it has completely removed the upperferromagnetic layer 55. In addition, etching should be carried out suchthat the P-TEOS film 38 remains more than 100 nm on the cap layer 56 andthe memory layer 55. The etching gas is a halogen gas containingchlorine or a carbon monoxide gas mixed with NH₃.

The P-TEOS film 39 (200 nm thick) is deposited over the entire uppersurface, as shown in FIG. 27A. Etch-back is performed on it to form theside wall 39 (as the etching mask) on the lateral surface of the freelayer 50, as shown in FIG. 27B.

The tunnel insulating film 54 and the pinned layer 60 are removed byreactive ion etching that employs as the mask the upper P-TEOS film 38covering the free layer 50 and the side wall 39 of P-TEOS, as shown inFIG. 27C. The etching gas is a halogen gas containing chlorine or acarbon monoxide gas mixed with NH₃.

The photoresist mask 41 is formed and the connecting hole 42 reachingthe plug 34 formed in the lower layer wiring 31 is made, as shown inFIG. 27D. The photoresist mask 41 is formed such that the P-TEOS film 38and the side wall 39 are partly exposed. The word line 12 existing belowthe TMR element 10 has its upper and lateral sides surrounded by anetch-selective material, and the insulating film 45 which has its topcovered with the P-TEOS film 38 and the side wall 39 remains unetchedwhen the connecting hole 42 is made. Consequently, the word line 12 isprotected more safely and the connecting hole 42 is formed close to theword line 12 easily by full-wafer etching. Thus, it is possible toreduce further the distance between the word line 12 and the localwiring (mentioned later) to be formed in the connecting hole 42.

With the resist mask 41 removed, the Cu film 49 is formed by sputteringover the entire upper surface, as shown in FIG. 28A. Etch-back isperformed on the Cu film 49 so as to remove the upper Cu film, as shownin FIG. 28B. The Cu film remains on the tunnel insulating film 54, thelateral surface of the pinned layer 60, and the side wall surface of theconnecting hole 42. The local wiring 22A is formed from the Cu filmwhich has remained, extending to one of the side wall surfaces of theconnecting hole 42.

CVD or PVD is performed to deposit the insulating film 48 of SiO₂ orAl₂O₃ over the entire surface, and CMP is performed to planarize andpolish the insulating film 48 and the P-TEOS film 38, so that the caplayer 56 (which is the uppermost layer of the TMR) is exposed, as shownin FIG. 28C. The exposed part functions as a self-aligned contact forthe bit line.

The bit line 11, the peripheral circuit wiring (not shown), and thebonding pad region (not shown) are formed by the standard wiringtechnology, as shown in FIG. 28D. The plasma silicon nitride film 46 isdeposited over the entire surface. Finally, a hole for the bonding padregion is made. Thus, the wafer process for LSI is completed.

Embodiment 4-2

The production process will be described with reference to FIGS. 29 to32.

On the lower layer wiring 31 (600 nm thick) are sequentially depositedthe HDP film 32 (800 nm thick) and the P-TEOS film 33 (1200 nm thick),as shown in FIG. 29A. Then, CMP is performed such that an insulting film(700 nm thick) is left on the lower layer wiring 31, as shown in FIG.29B.

The metal multi-layer film 36 (such as Ti/TiN/Al-0.5% Cu=10/30/700 nm)is deposited by sputtering, and then the P—SiN film 37 (100 nm thick) isdeposited, as shown in FIG. 29C. Etching though the photoresist film 41as the mask is performed on the P—SiN film 37 and the metal multi-layerfilm 36 in order to form the word line 12, as shown in FIG. 29D. In thisway it is possible to form the lower layer wiring 31 below the word line12.

The P—SiN film 47 (50 nm thick) is deposited and etch-back is performedon it, as shown in FIG. 29E. This step forms the side wall 47 of P—SiNon the lateral surface of the word line 12, as shown in FIG. 29F. Theamount of overetching should be set up so that the P—SiN film 37 remainsmore than 70 nm on the word line 12.

CVD or PVD is performed to deposit the insulating film 45 of SiO₂ orAl₂O₃ over the entire surface, and CMP is performed to planarize andpolish the insulating film 45, so that P—SiN film 37 is exposed, asshown in FIG. 30A.

PVD is carried out to sequentially form the pinned layer 60 (consistingof the barrier layer 51, the antiferromagnetic layer 52, and theferromagnetic layer 53) and the free layer 50 (consisting of the tunnelinsulating film 54, the ferromagnetic layer (memory layer) 55, and thecap layer 56) from the same materials as used in Embodiment 1, as shownin FIG. 30B.

The P-TEOS film 38 (200 nm thick) is deposited and then it is patternedby reactive ion etching through the photoresist film 43 as the mask, asshown in FIG. 30C. This P-TEOS film 38 functions as the etch-selectivefilm that covers the upper surface of the TMR element.

With the photoresist film removed, reactive ion etching is performed onthe free layer 50 (consisting of the cap layer 56 and the upperferromagnetic layer 55) through the P-TEOS film 38 as the mask, as shownin FIG. 30D. Etching should be carried out such that it terminates inthe tunnel insulating film 54 after it has completely removed the upperferromagnetic layer 55. In addition, etching should be carried out suchthat the P-TEOS film 38 remains more than 100 nm on the cap layer 56 andthe memory layer 55. The etching gas is a halogen gas containingchlorine or a carbon monoxide gas mixed with NH₃.

The P-TEOS film 39 (200 nm thick) is deposited over the entire uppersurface, as shown in FIG. 31A. Etch-back is performed on it to form theside wall 39 (as the etching mask) on the lateral surface of the freelayer 50, as shown in FIG. 31B.

The tunnel insulating film 54 and the pinned layer 60 are removed byreactive ion etching that employs as the mask the upper P-TEOS film 38covering the free layer 50 and the side wall 39 of P-TEOS, as shown inFIG. 31C. The etching gas is a halogen gas containing chlorine or acarbon monoxide gas mixed with NH₃.

The photoresist mask 41 is formed and the connecting hole 42 reachingthe lower layer wiring 31 is made, as shown in FIG. 31D. The photoresistmask 41 is formed such that the P-TEOS film 38 and the side wall 39 arepartly exposed. The word line 12 existing below the TMR element 10 hasits upper and lateral sides surrounded by an etch-selective material,and the insulating film 45 which has its top covered with the P-TEOSfilm 38 and the side wall 39 remains unetched when the connecting hole42 is made. Consequently, the word line 12 is protected more safely andthe connecting hole 42 is formed close to the word line 12 easily byfull-wafer etching. Thus, it is possible to form the local wiring(mentioned later) along the wall surface of the connecting hole 42.

With the resist mask 41 removed, the Cu film 49 is formed, for example,by sputtering over the entire upper surface, as shown in FIG. 32A.Etch-back is performed on the Cu film 49 so as to remove the upper Cufilm, as shown in FIG. 32B. The Cu film remains on the tunnel insulatingfilm 54, the lateral surface of the pinned layer 60, and the side wallsurface of the connecting hole 42. The local wiring 22A is formed fromthe Cu film which has remained, extending from the tunnel insulatingfilm 54 and the one side of the pinned layer 60 to one of the side wallsurfaces of the connecting hole 42. The distance between the word line12 and the local wiring 22A can be reduced.

CVD or PVD is performed to deposit the insulating film 48 of SiO₂ orAl₂O₃ over the entire surface, and CMP is performed to planarize andpolish the insulating film 48 and the P-TEOS film 38, so that the caplayer 56 (which is the uppermost layer of the TMR.) is exposed, as shownin FIG. 32C. The exposed part functions as a self-aligned contact forthe bit line.

The bit line 11, the peripheral circuit wiring (not shown), and thebonding pad region (not shown) are formed by the standard wiringtechnology, as shown in FIG. 32D. The plasma silicon nitride film 46 isdeposited over the entire surface. Finally, a hole for the bonding padregion is made. Thus, the wafer process for LSI is completed.

Embodiment 4 mentioned above offers the following advantages. The lowerlayer wiring 31 is formed below the word line 12. The upper surface 38and the lateral surface 39 of the free layer 50 of the TMR element 10are covered with a mask of etch-selective material. By using this maskand the resist mask 41 as the mask, the connecting hole 42 forconnection to the plug 34 formed on the lower layer wiring 31 is formed(in Embodiment 4-1). Alternatively, not only the mask of the uppersurface and lateral surface of the free layer 50 but also the uppersurface and lateral surface of the word line 12 are surrounded by anetch-selective material. By using the free layer 50 and the resist maskas the mask, the connecting hole 42 reaching the lower layer wiring 31is formed (in Embodiment 4-2). The reading wiring is formed with thelocal wiring 22A extending from the tunnel insulating film 54 and thelateral surface of the pinned layer 60 to the side wall surface of theconnecting hole 42, and it is connected to the lower layer wiring 31directly or through the plug 34.

However, since the upper surface and the lateral surface of the freelayer 50 of the TMR element 10 are covered with an etch-selective mask,it is possible to surely protect the word line 12 existing below thismask when the connecting hole 42 is formed (in Embodiment 4-1), and inthe case where the word line 12 itself is surrounded by anetch-selective material (in Embodiment 4-2), the word line 12 isprotected more surely. Therefore, it is possible to easily form theconnecting hole 42. In both cases, it is possible to reduce the distancebetween the connecting hole 42 and the word line 12. Since the regionbelow the connecting hole 42 shown in FIG. 1B is reduced, the size inthe direction along the bit line 11 is reduced as much as F and theconventional size 4F (shown in FIG. 39) can be reduced to 3F.

As the result, the MRAM region in the direction along the bit line canbe reduced, by 1F, to 3F (4F−1F) as in Embodiment 1, and the memory cellsize can be reduced to 9F2 (3F in the direction along the bit line×3F inthe direction intersecting the bit line). This result should be comparedwith the MRAM of conventional structure in which the region in thedirection along the bit line is 4F, as shown in FIG. 39.

The above-mentioned embodiments may be variously modified within thescope of the present invention.

For example, although the wiring pattern of the reading wiring 22 wasformed from the other layer (or the pinned layer 60 consisting of thetunnel insulating film 54, the ferromagnetic film 53, theantiferromagnetic layer 52, and the barrier layer 51) than the freelayer 50 (consisting of the cap layer 56 and the memory layer 55), it ispossible to form it with the pinned layer 60 or the barrier layer 51alone. In this way it is possible to place any other material than thatused for the reading wiring 22 in the position necessary for formationof the TMR element. This saves materials and simplifies steps.

The plug 34 formed on the lower wiring 31 may be omitted, and all can beconnected directly to the lower layer wiring 31 by extending the readingwiring 22.

The plug 34 may be formed by electroless plating as well as electrolyticplating (for damascene process). The Cu film 49 in Embodiment 3 may beformed by electrolytic plating (for damascene process) in place ofelectroless plating.

In Embodiments 3 and 4, an etch-selective material is placed on theupper and lateral surfaces of the TMR element 10, however, the materialon the upper surface may be omitted. Even though this material isabsent, the connecting hole 42 can be formed by covering the uppersurface entirely with the resist mask.

The production process and materials used in each embodiment may bereplaced by any adequate ones.

1. A magnetic memory device comprising: a plurality of tunnelmagnetoresistance effect elements, each comprising at least amagnetization pinned layer in which the direction of magnetization ispinned, a tunnel barrier layer, and a magnetic layer in which thedirection of magnetization is variable; a first conducting elementformed on one side of each tunnel magnetoresistance effect element witha first insulating layer interposed therebetween; and a secondconducting element formed on the other side of each tunnelmagnetoresistance effect element, wherein information is written intoeach tunnel magnetoresistance effect element by applying current to thefirst conducting element and also to the second conducting element, andwritten information is read out of each tunnel magnetoresistance effectelement through a read wiring having a connection to a secondary wiring,wherein the read wiring is comprised of a contiguous conductive materialformed during a different process than a process during which the firstand second conducting elements are formed, and wherein said secondarywiring is separated from said tunnel magnetoresistance effect element byat least a layer containing said first conductive element or said secondconductive element.
 2. The magnetic memory device as defined in claim 1,wherein the read wiring is connected to a conducting plug and saidconducting plug is further connected to the secondary wiring.
 3. Themagnetic memory device as defined in claim 1, wherein the read wiring isconnected to the secondary wiring by a local wiring.
 4. The magneticmemory device as defined in claim 3, wherein the read wiring isconnected to the secondary wiring through a first connecting hole and asecond connecting hole.
 5. The magnetic memory device as defined inclaim 2, wherein at least a portion of the conducting plug is formed ata same height as the first insulating layer.
 6. The magnetic memorydevice as defined in claim 2, wherein the conducting plug is formed at aheight which is lower than the first insulating layer.
 7. The magneticmemory device as defined in claim 1, wherein at least a lateral surfaceof a layer containing the first conducting element is covered with amaterial that is etch-selective for an etchant other than an etchantused to form the first conducting element.
 8. The magnetic memory deviceas defined in claim 1, wherein an upper constituent layer above themagnetization pinned layer of the tunnel magnetoresistance effectelement is patterned and at least a lateral surface of the pattern iscovered with a material which is etch-selective for a constituent layerbelow the upper constituent layer and a layer in which at least thefirst conducting element is embedded.
 9. The magnetic memory device asdefined in claim 1, which is constructed such that a second insulatinglayer is held between the magnetization pinned layer and the magneticlayer, and information is written by applying a current to a bit lineand a word line formed above and below the tunnel magnetoresistanceeffect element so that the current induces a magnetic field whichmagnetizes the magnetic layer in a prescribed direction, and writteninformation is read by the tunnel magnetoresistance effect through thesecond insulating layer as the tunnel barrier layer.
 10. A method forproducing a magnetic memory device having a plurality of tunnelmagnetoresistance effect elements, each comprising at least amagnetization pinned layer in which the direction of magnetization ispinned, a tunnel barrier layer, and a magnetic layer in which thedirection of magnetization is variable, such that information is writteninto the tunnel magnetoresistance effect element as current is appliedto a first conducting element formed on one side of the tunnelmagnetoresistance effect element with a first insulating layerinterposed therebetween and a second conducting element formed on theother side of the tunnel magnetoresistance effect element, whereinwritten information is read out of the tunnel magnetoresistance effectelement through a read wiring of the tunnel magnetoresistance effectelement which connects to a secondary wiring wherein the read wiring iscomprised of a contiguous conductive material formed during a differentprocess than a process during which the first and second conductingelements are formed, and wherein said secondary wiring is separated fromsaid tunnel magnetoresistance effect element by at least a layercontaining said first conductive element or said second conductiveelement, the method comprising: embedding a secondary wiring to beconnected to the read wiring in a second insulating layer, wherein thelayer containing the secondary wiring is formed so as to be separatedfrom the tunnel magnetoresistance effect element by at least said layercontaining said first conductive element or said layer containing saidsecond conductive element; forming a connecting hole in the layercontaining the first conducting element at a position offset from thefirst conducting element embedded therein; and connecting the readwiring through the connecting hole to the secondary wiring.
 11. Themethod for producing a magnetic memory device as defined in claim 10,wherein the read wiring is connected a conducting plug and saidconducting plug is further connected to the secondary wiring.
 12. Themethod for producing a magnetic memory device as defined in claim 10,wherein the read wiring is connected to the secondary wiring by a localwiring which covers a lateral side-surface of the tunnelmagnetoresistance effect element and extends down a wall surface of theconnecting hole to the secondary wiring.
 13. The method for producing amagnetic memory device as defined in claim 11, wherein the read wiringis connected through the connecting hole to the secondary wiring. 14.The method for producing a magnetic memory device as defined in claim11, wherein at least a portion of the conducting plug is formed a sameheight as the first insulating layer.
 15. The method for producing amagnetic memory device as defined in claim 11, wherein the conductingplug is formed at a height which is lower than the first insulatinglayer.
 16. The method for producing a magnetic memory device as definedin claim 10, wherein at least a lateral surface of a layer containingthe first conducting element is covered with a material which isetch-selective for a material other than the material used to form thefirst conducting element, and the connecting hole is formed byselectively etching at least the material present in the layercontaining the first conducting element other than the material used toform the first conducting element by using the coating material as themask.
 17. The method for producing a magnetic memory device as definedin claim 10, wherein an upper constituent layer above the magnetizationpinned layer of the tunnel magnetoresistance effect element is patternedand at least a lateral surface of the pattern is covered with a materialwhich is etch-selective for at least the constituent layer below theupper constituent layer and a layer containing the first conductingelement, and the second connecting hole is formed by selectively etchingthe at least lower constituent layer and the layer containing a firstconducting element by using the coating material as a mask.
 18. Themethod for producing a magnetic memory device as defined in claim 10,wherein the magnetic memory device is constructed such that aninsulating layer is held between the magnetization pinned layer and themagnetic layer, and information is written by applying a current to abit line and a word line formed above and below the tunnelmagnetoresistance effect element so that the current induces a magneticfield which magnetizes the magnetic layer in a prescribed direction, andwritten information is read by the tunnel magnetoresistance effectthrough the insulating layer as the tunnel barrier layer.